Large scale fluidic character display



Sept. 29, 1970 R. FQO'KEEFE 3,530,606.

v LARGE SCALE FLUIDIC CHARACTER DISPLAY Filed oct. 28, 196e 604 l 534 amm-warf.

United States Patent O 3 530,606 LARGE SCALE FLUIDIC CHARACTER DISPLAY Robert F. OKeefe, Trumbull, Conn., assignor to Pitney- Bowes, Inc., Stamford, Conn., a corporation of Dela- Ware Filed Oct. 28, 1968, Ser. No. 771,256 Int. Cl. G09f 9/30 U.S. Cl. 40'-28 9 Claims ABSTRACT OF THE DISCLOSURE In a large scale iiuidic character display of the type in which individual elements appear in different spatial patterns on a display face to form various alphanumeric characters, the elements are each divided into a plurality of sub-elements, and means are provided for insuring that all the sub-elements of an element act in unison for character display purposes. The sub-elements maybe either physically or fluidically linked to achieve this result. The area of the display face which is occupied by any one of the sub-elements is but a fraction of the area occupied Iby the entire element. The decrease in area overcomes the response speed limitations previously encountered with large scale alphanumeric character display devices.

FIELD OF THE INVENTION This invention relates generally to readout devices for displaying a succession of alphanumeric characters, and it is particularly concerned with a lluid driven display constructed on a large scale.

THE PRIOR ART Data processing and control apparatus has long employed readout `devices to display output information in alphanumeric form to the users of such equipment. The earliest such display devices were electrically driven, primarily because they Were designed for use with electronic computing and control circuitry. More recently, the de- -velopment of fluid switching and logic devices has lead to the proliferation of fluidic data handling and control equipment and a requirement for compatible character display devices.

In response to this need the type of duid driven character display device exemplied by U.S. Pat. No. 3,400,478 was developed by the present inventor. In that device a frame resembling a honeycomb has a display face and a plurality of apertures opening therethrough. The display face has a character display area which is divided into a plurality of elemental areas, each one of which contains a single aperture of the honeycomb frame. Within each aperture is a display element inthe form of a piston which reciprocates therein. Fluid pressure is used to drive some of the pistons to the front of the apertures so that they become visible at the display face, and others to the rear of the apertures so that they cannot be seen at the display face. Individual fluid lines are provided for the respective display elements, and are driven by individual iiuid switching devices to obtain the appropriate spatial pattern to portray the desired alphanumeric character or other symbol.

In small scale alphanumeric readouts of the type employed, for example, in a data processing or control console, the character display need only be large enough to be visible in the immediate vicinity. In such small scale applications, this type of display has been extremely successful. In particular, its speed of response is excellent, since the characters displayed can be changed faster than the human eye can follow. In addition, in a small scale display the amount of mass included in each of the dis- Patented Sept. 29, 1970 play elements is not excessive, and they can be accelerated rapidly between the visible position and the invisible position.

There are certain inherent limitations in this type of display device, however. It has been found that, in order for each individual display element to be rendered completely invisible, it must be retracted from the display face by a distance of about twice the diameter of the element. In small scale display devices, the element diameter is of the order of a minor fraction of an inch. Accordingly, the required travel of twice as much is still rather small, and the element mass is also small. lt is because of this short travel and small mass that small scale display devices can be switched with suicient speed for display purposes.

The limitations mentioned above become troublesome, however, when it is desired to produce a character display device for a large scale readout, e.g. a stock quotation or transportation arrival and departure information display, which must be large enough to be visible to a large room full of people. A display device on this scale built according to prior art concepts requires very large diameter display elements. This in turn requires a very large travel in order to preserve a ratio of 2:1 so that the display element is completely invisible in its retracted position. In addition, such large elements are massive; and the combination of massive elements moving over large distances unduly limits the response speed of the device.

SUMMARY AND OBJECTS OF THE INVENTION It is therefore a general object of this invention to provide a high speed, large scale readout device. More specifically, this invention has as its objective the provision of a fluidic character display device of the movable element type which can be scaled up` to large physical proportions without sacrificing fast response. Stated another way, the objective of this invention is to Iprovide a uidic character display device of this kind in which the effective element diameter is small even though the overall character proportions are greatly enlarged, so that travel distances are kept down to tolerable proportions and do not unduly limit the response speed of the device.

In carrying out the invention there is provided a large scale character display of the kind under discussion, in which each of the display elements comprises a plurality of sub-elements movable within the frame of the device from a position of visibility at the display face to a position of invisibility relative to the display face. In addition, means are provided for causing all the sub-elements of a display element to move in unison between the different visibility positions in response to iluid impulses on the individual uid line of the display element. As a result, each such group of sub-elements acts as a single display element. Yet each individual sub-element occupies a small fraction of the element on the display face, so as to reduce the amplitude of movement necessary between the positions of visibility and invisibility. The result is a fast response time, despite the large scale proportions of the overall character display.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. l is a front perspective view of a iluidic character display device in accordance with a preferred embodiment of the present invention.

FIG. 2 is a sectional view, taken along the lines 2 2 of FIG. 1.

FIG. 3 is a sectional view similar to FIG. 2, showing an alternative embodiment of the invention.

FIG. 4 is another sectional view similar to FIGS. 2 and 3, showing another alternative embodiment 0f the invention.

And FIG. is still another sectional view, similar to FIGS. 2-4, showing still another alternative embodiment of the invention.

The same reference characters refer to the same elments throughout the several 4views of the drawings; and reference characters having the same last two digits refer to corresponding elements in dilferent embodiments of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The iluidic character display device of FIGS. 1 and 2 generally comprises a large block 12 which constitutes the frame of the device, and which may be most conveniently molded from a single piece of conventional plastic material. Over the front of the frame 12 is secured a faceplate `14 of transparent material such as glass or clear plastic to permit the viewer to see an alphanumeric character displayed on the front face 16 of the frame 12. The display face 16 comprises a plurality of elemental areas 18, each of which contains a single display element of an alphanumeric character. In the particular example given, there are ve vertical columns and seven horizontai rows of elemental areas 18, phantom lines being provided in the drawing to separate the respective elemental areas for the purposes of illustration. Thus, the character display face 16 comprises a five by seven array of elements, and this array defines a single character position. In a typical display requiring more than one character, the display device 10 would be duplicated in horizontal rows, and possibly also in vertical columns, as many times as necessary to provide the proper number of character positions.

As in prior art devices, each individual display element 18 is turned on by fluid impulses (arrows 41) which move piston means forwardly within the frame 12 to a position of visibility at the display face 16. Individual fluid conduits 20 are provided for switching on each of the individual display elements 18 in this manner. The particular pattern of elements 18 which are on and off determines the particular alphanumeric character displayed at the moment. In the specific example of FIG. 1, the numeral 3 is displayed,

Also as in prior art devices, a common return line 22 is provided which delivers a constant fluid pressure (arrows 25) through a return duct 24 extending through the depth and across most of the breath of the frame 12. The pressure acts through a planar space 26 between the face plate 14 and the display face 16 to exert a continuous biasing pressure which pushes all the off display elements back from the display face 16 so that they are no longer visible to the viewer.

In accordance with the present invention, however, each of the elemental areas 18 of the character display face 16 contains a plurality of sub-elements, the location of which is determined by individual sub-element apertures 28. In the specific example illustrated, there is an array of four sub-element apertures horizontally by four sub-element apertures vertically in each elemental area 18. Each sub-element aperture 28 intersects the display face 16 at the front surface of the frame 12, and extends rearwardly from the display face into the depth of the frame. As best seen in FIG. 2 which provides a detailed view of a representative elemental area 18, the individual sub-element apertures 28 are separated by partitions 30 which are part of the frame `12. Partitions 32, which are also part of the frame block 12, separate the elemental areas 18 from each other and from the return pressure duct 24.

Within the sub-element apertures 28 ride small subelements in the form of pistons 34 which are reciprocable forwardly and rearwardly therein. Each sub-element piston 34 which is retracted to the rear of its respective subelement aperture 28 (the position illustrated in FIG. 2) is not visible at the display face 16. On the other hand,

each sub-element piston 34 may be made visible at the display face 1-6 by a fluid pulse (arrows 41) which driv'es it forwardly to the front of its individual sub-element aperture 28 so that the piston is visible through the transparent face plate 14. For maximum visibility, the pistons are brightly colored, at least over their front faces 42.

In order for each of the sub-elements Within a single elemental area 18 to operate as a Single display element, the frame 12 is formed with an element `aperture 36 immediately behind, and in communication with, each group of sub-element apertures 28. An element piston 38 reciprocates forwardly and rearwardly within each element aperture 36, and is secured to all of the sub-element pistons 34 of a particular elemental area 18. A uid conduit 40 extending rearwardly through the frame 12 from the element aperture 36 to the rear of the frame 12 is connected to the uid line 20 of that particular display element 18.

Accordingly, a fluid impulse (represented by arrows 41) arrives over a particular line 20 and drives its respective element piston 38 forwardly Within its element aperture 36, causing the associated sub-element pistons 34 to be driven forwardly within their respective subelement apertures 28 to a position of visibilty at the display face 16. The result is that a single fluid impulse on a single input line 20 makes visible all the sub-element pistons 34 of a given display element 18 by means of their common element piston 38. Similarly, all other display elements 18 which are required to be on in the display of a particular alphanumeric character are treated in a similar manner by means of a corresponding fluid impulse on their respective input lines 20. These fluid impulses are sustained as long as the character is displayed.

On the other hand, all those display elements 118 which are required to be off during the display of a particular alphanumeric character are not so driven; i.e. there is no fluid impulse on their respective input lines 20. The continuous pressure (represented by arrows 2S) communicated from the return line 22 and duct 24 to the planar space 26, produces a biasing force on the front surfaces 42 of the sub-element pistons 34. This force is not great enough to overcome the impulses 41 applied to the on pistons, but it drives the pistons 34 and 38 of the off display elements rearwardly to a position of invisibility relative to the display face 16. Then all that can be seen is the dark interior of the associated apertures 28, which contrasts with the brightly colored sur-faces 42 seen in other elemental areas. The return pressure Within the planar space 26 also serves to return a previously on display element 18 to its off condition when the switching impulse 41 terminates.

The front faces 42 of the sub-element pistons 34 are somewhat convexly curved so that even when these pistons are all the way forward, at least the margins of the forward faces 42 are out of contact with the transparent face plate 14, permitting the return uid pressure to bias the pistons rearwardly at the appropriate time. The space 26 is created by disposing the transparent face plate 14 somewhat forwardly of the display face 16. This is accomplished by providing the frame 12 with a border 44 to which the face plate 14 is cemented, the border 44 extending some distance beyond the partitions 30 and 32.

In the embodiment of FIGS. 1 and 2 the element piston 38 is in the form of a hollow cylinder. The term cylinder is used herein in its general sense, in 'which the cylinder can have any desired external cross-sectional shape, for example circular, square or rectangular. The cylinder is open at the rear end 46 thereof, and has a front member 48 closing olf the forward end. The 'group of sub-element pistons 34 within an element area 18 all extend forwardly from their associated front member 48. The entire assembly of the element piston 3-8 and its associated sub-element pistons 34 may be most conveniently fabricated from a single piece of molded plastic material of a conventional kind. AIf desired, a shoulder 50 may be formed in the frame 12 around the edges of the element aperture 36- in the plane where the sub-element apertures 28 open into the element aperture 36. This shoulder 50 cooperates with a shoulder 52 formed at the margin of the front face of the element piston 38, to limit the forward movement of the entire assembly 38, 34. The length of the sub-element pistons 34 should then be so selected that the rounded forward faces 42 thereof at least reach the forward ends of the sub-element apertures 28, and preferably protrude forwardly therefrom and touch or closely approach the transparent face plate 14 for maximum visibility when the display element 18 is switched on. Alternatively, the face plate 14 itself can serve to limit forward motion of the piston assembly.

At the rear of the element aperture 36, where` it joins the fluid conduit 40, there is an annular surface 54' cooperating with the rear end of the element piston 38 to limit the rearward motion thereof produced by the return pressure (arrows 25). If the surface 54 is so placed that when the element piston 38 is fully retracted, the subelement pistons 34 are not entirely retracted from the subelement apertures 2&8, as illustrated in FIG. 2, then the sub-element pistons remain keyed to the sub-element apertures to prevent unwanted rotation of the element pistons 3:8, and the cross-sectional shape of the element piston 38 may be circular if desired.

`On the other hand the limiting surface 54 may be set back far enough so that the sub-element pistons 34 are fully withdrawn from the sub-element apertures 28. In that case it is desirable for the cross-sectional shape of' the element pistons 38 to be non-circular to prevent rotation of the element piston in the element aperture 36, so that on the next forward movement of the element piston, the sub-element pistons 34 will again line up perfectly with their corresponding sub-element apertures 28. AIn either case the internal cross-sectional shape of the element aperture 36 must be substantially congruent with the external cross-sectional shape chosen for the element piston. Such congruence provides a close but slideable tit between the element piston 38 and the element aperture 36, so as to provide a fluid seal therebetween, yet permit the piston to reciprocate freely within its aperture.

The visible area o-f the sub-element pistons 34 is the front face 42, and it is the diameter of this visible piston face which determines the travel necessary for each Subelement piston to withdraw to a position of invisibility within its aperture 28. Since the diameter of the front face 42 of each individual sub-element piston is far smaller than the corresponding diameter of a single large piston required to occupy an entire display element 18 by itself, the required piston travel is reduced, in the same ratio as the diameter reduction. The result is a sharp reduction in the response .time of the device 10, so that the device can be scaled up to large proportions to provide a display which is legible from a distance without undue sacrifice in speed.

To the viewer, the present character display differs from prior art devices only in that each element which forms a part of an alphanumeric character is itself broken up into dots, somewhat in the nature of a half-tone print, However, from the distances at which a large scale alphanumeric display `device of this kind is intended to be viewed, these dots tend to merge into each other, so that each element in the character display will have an offwhite, unitary visual effect upon the observer.

FIG. 3 shows a typical display element 31`8 of a somewhat dilferent embodiment. The structure is basically similar similar to that of FIGS. l1 and 2. A transparent face plate 314 is secured to a border 344 of a frame 312. A return duct 324 provides continuous uid return pressure represented by arrows 325, and introduces that return pressure into the space 326 between the face plate 314 and the display face 316 of the frame 312. The frame is provided with sub-element apertures 328 which communicate with an element aperture 336. The sub-element apertures 328 of a display element are separated from each other by partitions 330, and separated from the return pressure duct 324 and adjacent display element areas by partitions 332. Sub-element pistons 334 with brightly colored, convexly curved front faces 342 reciprocate within the individual sub-element apertures 328, and are integral with an element piston 338 reciprocating within `the element aperture 336.

-In this embodiment, however, the element piston 338 comprises a solid cylindrical body 346 of circular crosssection in .this instance, which reciprocates with a corresponding shaped bore 337 at the rear of the element aperture 336. The individual uid line 320 of the display element 318 joins a il-uid conduit 340 which is formed in the frame 312 and communicates with the rear of the bore 337 to deliver a fluid switching impulse (arrow 341) to the body 346. At the forward end of the cylindrical body 346, the element piston 338 is formed with an enlarged lflange 348 which rides in an enlarged cavity 339 at the front of the element aperture 336. 4It is this enlarged front flange 348 which carries the integrally molded sub-element pistons 334 associated with the particular display element 318.

Shoulder 350 is provided for a purpose similar to the shoulder 50 of the preceeding embodiment. 'This cooperates with shoulder 352 on the margins of the front surface of the ange 348 to limit forward movement of the element piston 338. Limitation of rearward retraction of the element piston is provided by the abutment of the rear surface ofthe cylindrical body 346 against the annular rear wall 354 of the bore 337. Once again, the rotation of the piston assembly 338, 334 can be prevented either by preventing full retraction of the sub-element pistons 34 from their respective sub-element apertures 328, or by providing ange 348 with a non-circular external crosssectional -shape so that it is not rotatable relative to the mating internal cross-sectional shape of the aperture cavity 339. Alternatively, the cylinder 346 can be made noncircular, along with its mating bore 337.

FIG. 4 illustrates another embodiment in which the structure is basically similar. A frame 412 has a broder 444 to which is secured a transparent face plate 414. Behind the face plate is a return pressure -space 426 fed by a duct 424 extending through the frame 412. The return pressure is represented by arrows 425. The frame is provided with a group of sub-element apertures 428 comprising a display element 418. Partitions 430 separate the sub-element apertures 428 from each other, while partitions 432 separate the display elements 418 from each other and from the return pressure duct 424. Subelement pistons 434 with brightly colored, convexly curved front faces 442 reciprocate within the sub-element apertures 428, and are integrally molded with an element piston in the form of a plate 438 disposed parallel to the display face 416. The element piston 438 reciprocates within an element aperture 436, and is formed with a marginal shoulder 452 which engages a marginal shoulder 450 of the frame to limit forward movement of the piston. The rear margin of the piston 438 engages a marginal shoulder 454 to limit rearward motion.

In this embodiment the frame 412 is divided into a rear portion 413 and a separate front portion 415. Front portion 413 is formed with the rear end ofthe return pressure duct 424, the fluid impulse conduit 440, and a chamber 437. The front portion 415 is formed with the front end of the return pressure duct 424, the sub-element apertures 428 and the element aperture 436. An elastomeric sheet 460 in the form of a rubber diaphragm is stretched across the rear of the element aperture 436. 'Ihe edges of the sheet 460 are received within an annular recess 439 formed in the frame portion 413, around the edges of the chamber 437. In assembling the embodiment of FIG. 4, the diaphragm 460 is cemented within the annular recess 439 and the frame sections 413 and 415 are cemented together to anchor the diaphragm 460 in place.

The inherent resilience of the diaphragm 460 causes it to exert a continuous forward biasing force against the piston 438 by means of a plunger 446 located at the rear of the piston. This forward biasing force exerted by the diaphragm 460 assists the lluid switching impulse, represented by arrow 441, in driving the piston assembly forward for rendering the display element 418 visible at the display face 416. This iluid switching impulse is delivered by individual line 420 through conduit 440, and enters the chamber 437 to exert its pressure on the diaphragm 460, which in turn acts on plunger 446 and piston 438.

When the on impulse terminates, then the return pressure (arrows) 425 in duct 424 and space 426 drives the piston assembly back into its invisible position. When this happens, the plunger 446 distends the diaphragm 460 in a rearward direction as seen in FIG. 4, the chamber 437 providing the necessary room for the diaphragm to flex rearwardly.

In the embodiments of the preceding figures the subelement pistons were in each case mechanically connected together. However it is also possible for them to be mechanically independent of each other, yet act in unison by means of a common fluid input. In the embodiment of FIG. S the frame 512 once again has a border 544 to which a transparent face plate 14 is secured. A return pressure duct 524 is provided through which a steady return pressure represented by arrows S25 is applied to the space l526 between the face plate 514 and the display face 516. The switching impulse is delivered over an individual iluid line 520. The frame 512 is formed with individual sub-element apertures i528, each of which has an individual sub-element piston 534 reciprocable therein. Each piston has a brightly colored convex front face 542. Partitions 530 separate the adjacent sub-element apertures 528 of each display element 518, while partitions 532 separate the display elements S18 from each other and from the return pressure duct 524.

There is no mechanical connection between the subelement pistons 534, but the conduit 540 which receives the fluid switching impulse represented by arrow 541 has a plurality of branches which distribute the iluid impulse to all the sub-element pistons 534 of a single display element 518, so that they are driven forwardly into their visible position in unison. Thus the conduit 540 branches into a vertical conduit 600, which in turn branches into a plurality of forwardly directed horizontal conduits 602 to impulse the particular vertical bank of sub-element pistons 534 visible in FIG. 5, as well as sidewardly directed horizontal branch passages 604 which go to other vertical banks of sub-element pistons 534 within the same display element 518. As a result, a single iluid switching impulse 541 turns on the entire display element 518 by moving all its sub-element pistons in unison.

All sub-element pistons I534 of every other display element 518 which must be turned on at the same time to portray the desired alphanumeric character are similarly switched in unison by their respective lluid impulses. On the other hand, all display elements 518 which are required to be switched off for the particular alphanumeric character are not provided with fluid impulses 541. As a result, the return pressure represented by arrows 52S drives all the sub-element pistons 5314 of those display elements 518 to their retracted or invisible positions illustrated in FIG. 5. Similarly, when a display element 518 which has been on must then be turned olli the fluid impulse 541 terminates, whereupon the return pressure 525 biases all the sub-element pistons l534 back to their original invisible positions.

An additional advantage which the FIG. 5 embodiment has over the prior art resides in the fact that its response speed is further reduced, owing to the fact that the mass of each sub-element piston 534 is far less than the mass required for a single piston large enough to occupy the entire display element area 118, and also far less than the total mass of the element piston and sub-element piston assemblies of the preceding figures. As a result, each sub-element piston 534 can be more rapidly accelerated, and thus responds more quickly when switched from one position to another.

Thus, in each of its embodiments the present invention provides a way of sub-dividing each display clement into a plurality of sub-elements acting in unison, so as to achieve essentially the same character readout results with much smaller piston travel requirements. Consequently, much faster response speeds can be achieved with large scale display devices designed to be visible to a large room full of people.

Since the foregoing description and drawings are merely illustrative, the scope of protection of the invention has been more broadly stated in the following claims; and these should be liberally interpreted so as to obtain the benefit of all equivalents to which the invention is fairly entitled.

The invention claimed is: 1. In a large scale fluid-driven character display of the type having a frame, a display face on said frame including at least one character position, an array of elements at said character position, each element occupying an elemental area, said elements being individually movable within said frame from a position of visibility at said display face to a position of invisibility relative to said display face, means for connecting individual lluid lines to convey iluid impulses for moving respective display elements independently between said dilerent visibility positions so that selected spatial patterns of display elements can be made visible to portray respective characters at said display face, and means for subsequently returning said display elements to their original positions; the improvement wherein:

each of said display elements comprises a plurality of sub-elements movable within said frame from a position of visibility at said display face to a position of invisibility relative to said display face;

said character display comprises means for causing all of the sub-elements of a display element to move in unison between said different visibility positions in response to said lluid impulses on the individual iluid line of said display element whereby to act as a group for character display purposes;

and each of said sub-elements occupies a fraction of said elemental area whereby to reduce the amplitude of movement necessary between said positions 0f visibility and invisibility.

2. A character display as in claim 1 fwherein:

said means for causing said group of sub-elements to move in unison comprises means for connecting said individual lluid line of said display element in common to all sub-elements of said group.

3. A character display as in claim 2 wherein:

said frame is provided with a plurality of individual sub-element apertures adjacent said display face and extending transversely therefrom;

said sub-elements comprise individual sub-element pistons reciprocable within respective one of said subelement apertures between said positions of visibility and invisibility relative to said display face;

and said common connection comprises iluid conduit means formed in said frame and branching to connect the individual fluid line of a display element to deliver said fluid impulses to all the sub-element pistons within an elemental area.

4. A character display as in claim 1 wherein:

said means for causing said sub-elements to move in unison comprises a mechanical interconnection between the sub-elements of a display element.

5. A character display as in claim 4 wherein:

said frame is provided with a plurality of individual sub-element apertures adjacent said display face and extending transversely therefrom;

said sub-elements comprise individual sub-element pistons reciprocable Iwithin respective one of said subelement apertures between said positions of visibility and invisibility relative to said display face;

said frame is provided with respective element apertures at the ends remote from said display face of respective groups of sub-element apertures within the same elemental area;

and said mechanical interconnection comprises respective element pistons reciprocable transversely to said display face Within respective element apertures in response to said fluid impulses on the respective uid lines of respective display elements;

said element pistons being secured to each of the subelement pistons of their respective display elements whereby the element piston and its associated subelement piston-s of each display element move as a unit in response to said uid impulses.

6. A character `display as in claim 4 wherein:

said element pistons are hollow cylinders of any desired external cross-sectional shape, said cylinders being open at a rear end thereof remote from said display face and having a front face closing off the forward end of said cylinder;

said sub-element pistons of each display element eX- tending forwardly from said front face;

said element apertures having internal cross-sectional shapes substantially congruent lwith the external cross-sectional shapes of said element pistons.

7. A character display as in claim 4 wherein:

said element pistons comprise respective cylindrical bodies of any desired external cross-sectional shape, each having an enlarged flange at a forward end of said body;

said sub-element pistons of each display element extending forwardly from said flange;

said element apertures having a first internal crosssectional shape at the rear thereof which is substantially congruent Awith the external cross-sectional shape of said cylindrical body, and a second internal cross-sectional shape at the front thereof which is substantially congruent with the external cross-sectional shape of said flange.

8. A character display as in claim 4 wherein:

said element pistons comprise respective connecting plates extending substantially parallel to said display face;

said sub-element pistons of each display element extending forwardly from said connecting plate toward said display face;

and said element apertures being formed with internal cross-sectional shapes substantially congruent with the external cross-sectional shape of said connecting plates.

9. A character display as in claim 8 further comprising:

an elastomeric sheet behind each connecting plate and substantially parallel thereto;

means for clamping the edges of said sheet for anchoring it in place relative to said frame;

and a plunger at the rear of said connecting plate engaging a central region of said sheet and rearwardly distending the material thereof whereby said sheets bias their respective element piston and associated sub-element pistons forwardly toward said display face;

-said element apertures including space for said respective sheets to dstend rearwardly therein;

said individual Huid lines being connected to introduce said fluid impulses rearwardly of the respective elastomeric sheets of each display element whereby to a-ssist said sheet in propelling said pistons forwardly toward said display face for character display purposes.

References Cited UNITED STATES PATENTS 3,106,794 10/1963 Le Golf 40-28 3,249,302 5/1966 Bowles 40-28 X 3,395,471 8/1968 Rydstrom 40-28 3,391,480 7/1968 OKeefe 40-28 3,400,478 9/ 1968 OKeefe 40--28 40 EUGENE R. CAPOZIO, Primary Examiner W. J. CONTRERAS, Assistant Examiner 

